The structure of the lac promoter will be further analyzed by (1) determining the sequence changes caused by a variety of lac promoter mutations, (2) establishing a system for in vitro directed mutagenesis of the lac promoter restriction fragment in order to generate more promoter mutations, and (3) analyzing the effect of promoter mutations on RNA polymerase binding and transcription initiation. The structure of other genetic regions will be studied such as the tet promoter.